Note: Descriptions are shown in the official language in which they were submitted.
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Shaving device with improved contour following
FIELD OF THE INVENTION
The present invention relates to a shaving head for use in a shaving device
for
removing hairs from skin by cutting through the hairs, comprising at least one
cutting unit,
and a holder for holding the cutting unit, which holder is intended to be
mounted on a body
portion of the shaving device, which body portion is intended to be taken hold
of by a user of
the shaving device, and serves for accommodating various members of the
shaving device,
wherein the cutting unit comprises an external cutting member having a
surface which is intended for contacting skin during a shaving action, and
which is
interrupted by openings for allowing hairs to pass, wherein the cutting unit
further comprises
an internal cutting member which is drivable for movement along the openings
in the surface
of the external cutting member, and which is adapted to cut through hairs
during such
movement,
wherein the external cutting member is suspended relative to the holder
through suspension means comprising:
- a suspension member, and
- a pivot construction by means of which the suspension member is pivotable
relative to the holder.
Furthermore, the present invention relates to a shaving device for removing
hairs from skin by cutting through the hairs, comprising a body portion which
is intended to
be taken hold of by a user of the shaving device, and which serves for
accommodating
various members of the shaving device, and a shaving head as mentioned.
BACKGROUND OF THE INVENTION
An example of a shaving device comprising a body portion, and a shaving
head having at least one cutting unit and a holder as described above is known
from WO
2006/067721. The shaving device is a so-called rotary shaving device, i.e. a
shaving device in
which the internal cutting member comprises a ring-shaped support portion
which is provided
with a number of cutting blades, wherein the support portion is driven such as
to rotate
during operation of the shaving device. In the example known from WO
2006/067721, the
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shaving head of the shaving device is equipped with three cutting units. The
external cutting
member of the cutting units is shaped like a cap which serves for covering the
internal cutting
member, which is intended to be used for contacting portions of skin to be
subjected to a
shaving action, and which is provided with openings for letting through hairs
from the
portions of skin to the cutting blades of the internal cutting member. It is
understood that a
main function of the external cutting member is avoiding direct contact
between the cutting
blades of the internal cutting member and the portions of skin, so that skin
damage is
prevented.
The shaving device comprises means such as a motor for driving the internal
cutting members. Proper use of the shaving device involves movement of the
shaving device
in such a way that a surface of the external cutting members glides over
portions of skin. In
the process, hairs protruding from the skin are continuously caught in the
openings of the
external cutting members and are cut through as soon as they are encountered
by the moving
cutting blades of the internal cutting members, wherein edges of the openings
of the external
cutting member serve as counter cutting edges.
In each of the cutting units, the external cutting member is suspended
relative
to the holder through a suspension member. The suspension member has a
generally circular
shape, and is tiltable relative to the holder about a tilting axis. The three
cutting units are
arranged in a symmetrical configuration about a central axis, and means for
driving the
internal cutting members of the cutting units comprise a central drive shaft,
a gear wheel
arranged on the drive shaft, and a gear wheel per cutting unit. The central
gear wheel is
arranged such as to engage all three gear wheels of the cutting units and
drive these gear
wheels. The tilting axes of the suspension members of the cutting units extend
in an area
where the gear wheels of the cutting members engage the central gear wheel,
i.e. in an area
closer to the circumference of the cutting units than to a central position.
Although the use of the shaving device known from WO 2006/067721 yields
good shaving results, there is a need for further improvement. A number of
disadvantages
appear to be associated with the shaving device. For example, when the shaving
device is
applied for a shaving action on the face, following the facial contours
involves tilting
movements of the suspension members of the cutting units about their tilting
axes. In the
process, it appears that a reaction on the skin involves a sliding effect,
which results in
frequently changing stretching and compressing of the skin. Furthermore, there
appears to be
a non-uniform skin pressure distribution between skin and cutting units. Also,
it is only
possible to closely follow purely convex and concave contours.
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SUMMARY OF THE INVENTION
It is an object of the present invention to improve the shaving results and
the
feel experienced by a user of the shaving device by eliminating the above-
mentioned
disadvantages. The object is achieved by providing a shaving head in which the
means for
suspending the external cutting member relative to the holder of the shaving
head comprise a
second pivot construction, by means of which the external cutting member is
pivotable
relative to the suspension member, in addition to the suspension member and
the first pivot
construction by means of which the suspension member is pivotable relative to
the holder,
wherein a pivoting stiffness of the second pivot construction is lower than a
pivoting stiffness
of the first pivot construction.
For the sake of clarity, it is noted that the pivoting stiffness is directly
related
to a tilting momentum that is needed to realize a defined tilting angle in a
pivot construction.
The higher the tilting momentum needed to realize a defined tilting angle, the
higher the
pivoting stiffness. This may be realized on the basis of a steeper relation
between the tilting
momentum and the tilting angle, but it is also possible that there is a
threshold value of the
tilting momentum, which needs to be exerted before a tilting movement and a
tilting angle
may actually be realized. In such a case, according to the present invention,
the threshold
value as mentioned is lower for the second pivot construction than for the
first pivot
construction. The possibility of having a threshold value of the tilting
momentum may also
be denoted as prestress in a pivot connection, wherein a pivoting stiffness is
higher when it
takes a higher momentum to move a pivotably arranged member from a default
rest position.
In comparison with the shaving head of the shaving device known from WO
2006/067721, the at least one cutting unit of the shaving head according to
the present
invention does not only comprise a first pivot construction for realizing a
pivoting
arrangement of the suspension member with respect to the holder, but also a
second pivot
construction for realizing a pivoting arrangement of the external cutting
member with respect
to the suspension member.
Within the scope of the present invention, the number of pivot constructions
of
the suspension means may be any desired number. In a practical embodiment of
the shaving
head according to the present invention, there may be at least one additional
suspension
member besides the suspension member which is located at the side of the
holder. In the
following, for the sake of clarity, the suspension member which is located at
the side of the
holder will be denoted as basic suspension member. In case the suspension
means comprise
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two or more suspension members, the suspension member which is located at the
side of the
external cutting member will be denoted as end suspension member, and any
other
suspension member, besides the basic suspension member and the end suspension
member,
will be denoted as intermediate suspension member.
For example, the suspension means of the shaving head according to the
present invention may comprise two suspension members, wherein the end
suspension
member is pivotable relative to the basic suspension member by means of the
second pivot
construction as defined in the foregoing. According to another possibility
existing within the
scope of the present invention, there are three pivot constructions and two
suspension
members in the suspension means, wherein the end suspension member is
pivotable relative
to the basic suspension member by means of the second pivot construction,
wherein the
external cutting member is pivotable relative to the end suspension member by
means of a
third pivot construction, and wherein both the pivoting stiffness of the
second pivot
construction and a pivoting stiffness of the third pivot construction are
lower than the
pivoting stiffness of the first pivot construction.
In any case, having suspension means comprising at least two pivot
constructions makes it possible to have a tilting axis which has a more or
less central position
in the cutting unit, and which is relatively close to skin level. Hence, the
application of at
least one additional pivot construction may solve most of the problems as
mentioned in the
foregoing, particularly the sliding effect on the skin and the non-uniform
pressure distribution
on the cutting unit. Furthermore, the contour following capability of the
cutting unit is
improved to an unexpectedly large extent by making sure that a pivoting
stiffness of a pivot
construction other than the first pivot construction is lower than a pivoting
stiffness of the
first pivot construction. An explanation can be found in the observation that
a momentum
which is needed to rotate a member suspended with low pivoting stiffness is
lower than a
momentum which is needed to rotate a member with high pivoting stiffness, so
that it is
possible to have both good contour following capabilities in an area of
relatively small
curvature changes, such as within the cheek or neck area of a user's skin, and
good contour
following capabilities in an area of larger curvature changes, such as between
cheek and neck
area.
All in all, when the present invention is applied, contour following is
improved to a surprisingly large extent. Furthermore, it is possible to
realize a situation in
which necessary skin pressure for optimal shaving performance of a shaving
device is less
user-dependent. Also, sensitivity to friction between skin and cutting unit
may be relatively
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low when the tilting axis of the at least one additional pivot construction
extends close to or
at skin level, and more uniform skin contact may be obtained when the tilting
axes of the
various pivot constructions extend in mutually different directions.
In a practical embodiment of the shaving head according to the present
invention comprising at least two suspension members, the suspension members
may
comprise rings which are connected to each other in a concentric arrangement
at two places
defining a tilting axis of the suspension members with respect to each other.
In other words,
the suspension members may be interconnected in a kind of cardanic
arrangement. Having
the suspension members in such an arrangement is a very practical manner of
realizing
desired tilting axes and degrees of freedom in the suspension of the external
cutting member
and the associated internal cutting member.
It is possible for the end suspension member to cover at least a portion of
the
other suspension member(s). An advantage of such a configuration is that the
feel of the
cutting units may be improved, assuming a situation in which the external
cutting member is
surrounded by the various suspension members. In such a situation, on the
basis of a covering
function of the end suspension member, it is achieved that a user of the
shaving device
comprising the shaving head according to the present invention experiences a
smooth surface
rather than a surface in which transitions between various suspension members
are present.
The present invention is very well applicable in the field of rotary shaving
devices, i.e. shaving devices in which the at least one internal cutting
member is rotatably
arranged. However, that does not alter the fact that types of movement of the
internal cutting
member other than a rotary movement are feasible within the scope of the
present invention.
The above-described and other aspects of the present invention will be
apparent from and elucidated with reference to the following detailed
description of a
shaving device and shaving heads for use in a shaving device, particularly
cutting units of the
shaving heads.
BRIEF DESCRIPTION OF THE DRAWINGS
The present invention will now be explained in greater detail with reference
to
the Figures, in which equal or similar parts are indicated by the same
reference signs, and in
which:
Figure 1 diagrammatically shows a perspective view of a shaving device
known per se;
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Figure 2 diagrammatically shows a perspective view of a shaving head
according to the present invention;
Figure 3 diagrammatically shows a perspective view of a section of a cutting
unit of a shaving head according to the present invention;
Figure 4 illustrates the degrees of freedom of a movement of a cutting unit of
a
shaving head according to the present invention;
Figures 5 and 6 diagrammatically show views of an alternative shaving head,
in which an end suspension member of the cutting units is adapted to cover a
portion of a
basic suspension member; and
Figures 7, 8 and 9 diagrammatically show views of another alternative shaving
head, in which an end suspension member of the cutting units is adapted to
completely cover
a basic suspension member.
DETAILED DESCRIPTION OF EMBODIMENTS
Figure 1 shows a conventional shaving device 1 such as known from WO
2006/067721. The shaving device 1 is a rotary shaving device in which a
shaving action is
realized by using rotating components. Another well-known type of shaving
device is a
device in which a shaving action is realized by using reciprocating
components. For the sake
of completeness, it is noted that the present invention is applicable in
various types of
shaving devices.
The shaving device 1 comprises a body portion 2 and a shaving head 3 in
which a number of cutting units 4 are located. The body portion 2 is intended
to be taken
hold of by a user of the shaving device 1, while the cutting units 4 are
intended to be
positioned against skin which is to be subjected to a shaving action, for
actually performing a
shaving action. In the shown example, the shaving head 3 has three cutting
units 4.
Each cutting unit 4 comprises an external cutting member 5 which is shaped
like a cap having an external skin contacting surface 6 and openings 7 for
letting through
hairs to an inside of the cutting unit 4, and an internal cutting member (not
shown) having a
number of cutting blades which are positioned in an inside space of the
cutting unit 4 on a
suitable support portion, and which are adapted to cut off the hairs. During
operation of the
shaving device 1, the support portion having the cutting blades is driven such
as to rotate. To
this end, the shaving device 1 may be equipped with any suitable driving means
(not shown)
such as a small electric motor.
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The operation of a shaving device 1 comprising a shaving head 3 having one
or more cutting units 4, wherein each of the cutting units 4 comprises an
external cutting
member 5 and an internal cutting member as described in the foregoing, is as
follows. When
the shaving device 1 is used for performing a shaving action, the external
cutting members 5
are moved across a portion of skin to be subjected to the shaving action by a
user of the
shaving device 1, and the internal cutting members are driven such as to
rotate at their
position right behind the external cutting members 5. Due to the movement of
the cutting
units 4 with respect to the skin, there is a continuous process of hairs
getting trapped inside
the openings 7 of the external cutting members 5 and being encountered by the
cutting blades
of the internal cutting members, as a result of which the hairs are cut
through.
The shaving device 1 comprises a holder 8 for holding the cutting units 4 and
mounting the shaving head 3 on the body portion 2. Furthermore, in the
conventional
situation as illustrated in Figure 1, each of the cutting units 4 comprises a
suspension ring 9
for realizing a pivot connection between the external cutting member 5 and the
holder 8,
wherein a tilting axis extends in a circumferential area of the cutting unit
4, at a side of the
cutting unit 4 which is near a central axis of the shaving head 3. By having
the tilting axis in
a structure extending from the body portion 2 to the external cutting member
5, the external
cutting member 5 and the associated internal cutting member are allowed to
follow a given
curvature of skin to be subjected to a shaving action.
The present invention relates to the way in which the external cutting members
of the cutting units 4 are suspended relative to the holder 8. Figure 2 shows
an embodiment
of a shaving head 3 according to the present invention. In comparison with the
conventional
situation, each cutting unit 4 comprises two suspension rings 9, 10 instead of
just one. In
particular, there is a basic suspension ring 9 which is comparable to the
suspension ring 9
which is present in the conventional situation. This basic suspension ring 9
is an outer ring
which is tiltable about a tilting axis located in a circumferential area of
the cutting unit 4.
Inside the basic suspension ring 9, in a concentric arrangement, another
suspension ring 10 is
arranged, and in this suspension ring l0the external cutting member 5 is
arranged. The basic
suspension ring 9 is pivotably connected to the holder 8, and the additional
suspension ring
10, which is also denoted as end suspension ring 10, is pivotably connected to
the basic
suspension ring 9.
In Figure 3, the configuration of the external cutting member 5 and the
suspension rings 9, 10 is clearly illustrated. In the concentric arrangement
as mentioned, the
suspension rings 9, 10 are connected to each other at two places which are
located on an
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imaginary straight line intersecting the centre of the concentric arrangement,
and in this way,
the pivot connection between the suspension rings 9, 10 is obtained. For the
sake of
completeness, it is noted that in the diagrammatic depiction in Figure 3,
details like the
openings 7 in the skin contacting surface 6 of the external cutting member 5
are not shown.
Figure 4 serves to illustrate the various degrees of freedom of movement of a
cutting unit 4, which are obtained when at least one additional suspension
ring 10 is applied
for suspending the external cutting member 5 relative to the holder 8. In the
first place, the
holder 8 is adapted to allow for rotational movements with respect to the body
portion 2,
which is only partially shown in figure 4, about two perpendicular tilting
axes a, b. In the
second place, the basic suspension ring 9 is tiltable with respect to the
holder 8 about a tilting
axis c. In the shown example, this tilting axis c extends substantially
parallel to one of the
tilting axes a, b of the holder 8. In the third place, the end suspension ring
10 is tiltable with
respect to the basic suspension ring 9 about a tilting axis d, which, in the
shown example,
extends substantially parallel to the tilting axis c of the basic suspension
ring 9 and one of the
tilting axes a, b of the holder 8. Furthermore, Figure 4 clearly shows that in
the shown
example, the tilting axis c of the basic suspension ring 9 has an off-centre
position with
respect to the cutting unit 4 and the external cutting member 5, whereas the
relative position
as mentioned of the tilting axis d of the end suspension ring 10 is a central
one. In the fourth
place, the external cutting member 5 is tiltable with respect to the end
suspension ring 10
about a tilting axis e, which, in the shown example, extends perpendicularly
to the tilting axes
c, d of the suspensions rings 9, 10.
In view of the overall construction of the shaving device 1 and the desired
application of the shaving device 1, it will be understood that there is only
a need for tilting
movements of the holder 8 and the suspension rings 9, 10 in limited ranges.
For example, the
tilting movements of the holder 8 may be in a range of 10 in two opposite
rotational
directions, starting from a default position of the holder 8, and the tilting
movements of the
basic suspension ring 9 may be in a range of 10 in only one rotational
direction, starting
from a default position of the basic suspension ring 9, and the tilting
movements of the end
suspension ring 10 may be in a range of 7 in two opposite rotational
directions, starting from
a default position of the end suspension ring 10.
In the shaving device 1 according to the present invention, the extent to
which
the contours of skin to be subjected to a shaving action can be followed is
improved. In this
respect, it is noted that an important feature of the suspension configuration
in which at least
two members 9, 10 which are tiltable with respect to each other are present is
that a stiffness
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of the pivot connection of the suspension members 9, 10 with respect to each
other is lower
than a stiffness of the pivot connection of the basic suspension member 9 to
the holder 8.
Hence, the momentum needed to rotate the end suspension member 10 is much
lower than
the momentum needed to rotate the basic suspension member 9. An advantage of
this fact
appears to be that a good contour following performance is obtained at two
levels, namely at
the level of an area of relatively small curvature changes and at the level of
an area of
relatively large curvature changes, wherein the end suspension member 10 is
primarily the
member which allows for coverage of the first area, and wherein the basic
suspension
member 9 is primarily the member which allows for coverage of the latter area.
Another factor contributing to contour following is to have a tilting axis
which
is closer to skin level. In the shown example, the tilting axis d of the end
suspension ring 10
with respect to the basic suspension ring 9 is closer to skin level than the
tilting axis c of the
basic suspension ring 9 with respect to the holder 8. On the basis of this
fact, contour
following is improved with respect to a situation in which there is only a
basic suspension
ring 9, i.e. the end suspension ring 10 is omitted. When a tilting axis is
closer to skin level,
the extent to which the external cutting member 5 slides over the skin during
a rotation of the
member 9, 10 tilting about the tilting axis is reduced, and the sensitivity to
friction forces is
reduced as well.
The tilting axes c, d of the various suspension members 9, 10 may be parallel,
as is the case in the shown example, but may also have a mutually different
orientation, even
perpendicular to one another. Another possibility is that there are more than
two suspension
members 9, 10, wherein an end suspension member 10 and an underlying
intermediate
suspension member may be tiltable in perpendicular directions. When pivot
connections are
realized in various directions, the capability of contour following in the
various directions is
obtained, which is improved contour following with respect to a situation of
movability in
fewer directions.
Figures 5 and 6 show a first alternative design of the cutting units 4. When
compared to the design of the cutting units 4 shown in Figures 2-4, the shape
of the end
suspension member 10 has changed. In particular, a portion 11 of the end
suspension member
is shaped such as to cover a portion of the underlying basic suspension member
9, as seen
from a side where contact between the cutting units 4 and the skin is to take
place. In the
shown example, this portion 11 is a portion which is at a side of the end
suspension member
10 facing away from the centre of the shaving head 3.
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With the alternative design of the end suspension member 10, the way in
which the feel of the shaving units 4 is experienced by a user of the shaving
device 1 is
improved. The reason is that with the enlarged portion 11 of the end
suspension member 10,
a smooth skin contacting surface is realized, wherein a length of a transition
between the end
suspension member 10 and the basic suspension member 9 is covered and thereby
prevented
from contacting skin. In that way, the possibility of a smooth gliding of the
external cutting
members 5 and the surrounding structures over the skin is enhanced.
Figures 7, 8 and 9 show a second alternative design of the cutting units 4.
According to this design, the end suspension member 10 is capable of
completely covering
the basic suspension member 9, so that there is no longer a transition between
the suspension
members 9, 10 where contact to the skin may take place.
It will be clear to a person skilled in the art that the scope of the present
invention is not limited to the examples discussed in the foregoing, but that
several
amendments and modifications thereof are possible without deviating from the
scope of the
present invention as defined in the attached claims. While the present
invention has been
illustrated and described in detail in the Figures and the description, such
illustration and
description are to be considered illustrative or exemplary only, and not
restrictive. The
present invention is not limited to the disclosed embodiments.
Variations to the disclosed embodiments can be understood and effected by a
person skilled in the art in practicing the claimed invention, from a study of
the Figures, the
description and the attached claims. In the claims, the word "comprising" does
not exclude
other steps or elements, and the indefinite article "a" or "an" does not
exclude a plurality. The
mere fact that certain measures are recited in mutually different dependent
claims does not
indicate that a combination of these measures cannot be used to advantage. Any
reference
signs in the claims should not be construed as limiting the scope of the
present invention.
It is noted that the designs of a cutting unit 4 of the shaving device 1
according
to the present invention as shown in the Figures, i.e. designs with suspension
members 9, 10
comprising rings in a concentric arrangement, allow for a compact structure of
the cutting
unit 4. Nevertheless, other shapes and configurations of the suspension
members 9, 10 are
feasible as well, as long as these members 9, 10 are capable of constituting a
connection
between the holder 8 and the external cutting member 5, wherein there is a
pivot connection
both at the location of the connection of the suspension members 9, 10 to the
holder 8 and at
the location where two suspension members 9, 10 are connected to each other,
and wherein a
pivoting stiffness of the latter connection is lower than a pivoting stiffness
of the first
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connection. When the suspension means of the shaving unit 4 comprise more than
two
suspension members, it is important that a stiffness of a pivoting arrangement
of a suspension
member is lower at a level which is further away from the holder 8 of the
shaving device 1
than at a level which is closest to the holder 8.
For the sake of completeness, it is noted that the cutting units 4 may be
arranged such as to be detachable with respect to the body portion 2 of the
shaving device 1.
For example, it may be possible for a user to remove the entire shaving head 3
from the body
portion 2 for cleaning purposes, wherein the connection between the holder 8
of the shaving
head 3 and the body portion 2 may be realized in any suitable manner for
allowing easy
detachment and attachment.
In a shaving device 1 comprising more than one cutting unit 4, it is possible
for the pivoting stiffness of pivot constructions to vary from cutting unit 4
to cutting unit 4. In
other words, the pivoting stiffness of the pivot constructions of one cutting
unit 4 does not
necessarily need to be the same as the pivoting stiffness of similar pivot
constructions of
another cutting unit 4. Nevertheless, in a shaving device 1, it is preferred
that all cutting units
4 are constructed according to the present invention, namely in such a way
that a stiffness of
a pivoting arrangement of a suspension member of the cutting unit 4 is lower
at a level which
is further away from a holder 8 of the shaving device 1 than at a level which
is closest to the
holder 8, as has been explained in the foregoing.
The present invention can be summarized as follows. A shaving head 3 for use
in a shaving device 1 comprises at least one cutting unit 4 in which an
external cutting
member 5 and an internal cutting member are arranged. In particular, the
internal cutting
member is movably arranged, and the internal cutting member is adapted to
perform a cutting
action on hairs when moving with respect to the hairs. The external cutting
member 5 serves
for contacting skin to be subjected to a shaving action, and allowing hairs to
pass from the
skin to the internal cutting member. To this end, the external cutting member
5 may be
shaped like a cap covering the internal cutting member, which cap is provided
with openings
7.
In addition to the cutting unit 4, the shaving head 3 comprises a holder 8 for
mounting the cutting unit 4 on a body portion 2 of a shaving device 1. For the
purpose of
suspending the external cutting member 5 relative to the holder 8, suspension
means are
provided. According to the present invention, the suspension means comprise at
least two
pivot constructions, wherein one pivot construction enables a member of the
suspension
means to be pivotable relative to the holder, and wherein another pivot
construction enables
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the external cutting member to be pivotable relative to the suspension member
as mentioned.
Furthermore, a pivoting stiffness of a connection of the latter pivot
construction is lower than
a pivoting stiffness of the first pivot construction.
On the basis of the features of the suspension means as mentioned, skin
contour following is improved, wherein good contour following performance is
obtained at
two levels, namely at the level of an area of relatively small curvature
changes and at the
level of an area of relatively large curvature changes .
